The invention relates to ground fault detectors and static discharge wriststrap monitors.
Along with the ever expanding utilization of electrostatic sensitive electronic components and assemblies is the need to protect such devices during handling and use. One of the more common techniques is for the person handling such devices to wear a conductive wriststrap that is connected to earth ground. Also, grounded workbenches, tables and the like are commonly used. Such work areas typically include a conductive surface made of carbon impregnated foam rubber or plastic that is connected to earth ground.
Since a wriststrap essentially tethers a user to a specific location, it is often desirable to provide a wriststrap that can be grounded through a conventional three-plug power outlet or any outlet that provides an earth ground return line. This provides the user increased mobility and avoids the need to work in only one location.
Power outlets, however, can be and sometimes are miswired. For example, the hot and neutral or ground lines may be reversed, or the earth ground connection may be of high resistance or even completely open. Such conditions are not only hazardous to someone using the outlet, but also prevent a true ground on the wriststrap thereby defeating the electrostatic protection the wriststrap would otherwise provide.